A slight amount of contamination derived from a rubber component or compounding agent adheres to a molding surface of a mold for vulcanizing rubber products such as tires or the like every time vulcanization is performed. Contamination gradually accumulates as the mold is used repeatedly, and therefore, leaving the contamination as is negatively impacts the quality of the products to be vulcanized. Therefore, as appropriate, the contamination needs to be removed by cleaning the molding surface. Examples of known mold cleaning methods include shot blasting cleaning methods, laser beam cleaning methods, plasma cleaning methods, and the like.
With a shot blasting cleaning method, the molding surface is easily scratched, and therefore, a laser beam cleaning method where a laser beam is irradiated on the molding surface to remove contamination by a shock wave, or a plasma cleaning method where contamination is chemically reacted and removed by a generated plasma is preferably used in order to prevent scratches on the molding surface caused by cleaning. However, an area that the plasma cleaning method can clean per unit time is small, and therefore, the laser beam cleaning method is more preferable when considering efficiency.
Various mold cleaning methods using a laser beam have been proposed (for example, refer to Japanese Patent Publication Nos. 2008-62633 and 2004-167744). In a cleaning method described in Japanese Patent Publication No. 2008-62633, contamination is removed by irradiating a laser beam (CO2 laser beam) supplied from a laser oscillator on a molding surface of a mold. At this time, an arm (manipulator) that moves the laser head is controlled by original shape data (CAD data and the like) of the mold and position correcting means for the laser head, and the arm moves the laser head along recesses and protrusions on the molding surface (refer to paragraphs [0011] and [0021] to and the like in Japanese Patent Publication No. 2008-62633).
However, the molding surface of the mold is not always formed in the same shape and is formed in various shapes. Therefore, in the method described in Japanese Patent Publication No. 2008-62633, in order to clean molds having different molding-surface shapes, an operation for invoking the original shape data of the mold stored in a control device is required every time mold cleaning is performed. For tire vulcanization molds which include a large variety of molding-surface shapes, there is a problem that checking whether the mold to be cleaned and the original shape data thereof mutually correspond is required every time cleaning is performed, and thus the operation is complicated.
In a cleaning method described in Japanese Patent Publication No. 2004-167744, a laser irradiator is fixed at a predetermined position, and a mold is rotated to move the mold such that the mold surface changes from a vertical orientation to an inclined orientation with regard to an optical axis of the laser beam. A process such as teaching this movement in advance or the like is required in order to rotate the mold in this manner.